Electrical apparatus



Oct. 3, 1944. G. HoLsT ET'AL 2,359,645

ELECTRICAL APPARATUS Filed Jan. 15, 1941 Patented Oct. 3, 1944 ELECTRICAL APPARATUS Gilles Holst and Johannes Hoekstra, Eindhoven,

Netherlands; vested in the Alien Property Custodian Application January 15, 1941, Serial No. 374,560

In the Netherlands September 6, 1939 In electric apparatus such as transformers which are housed in a casing the sealing oi this casing is naturally very important, especially' ii the casing is to be filled with a more or less liquid impregnating material.

Even if careful attention is given to the sealing oi the casmg there is always the danger that mechanical damage or repeated heating and cooling of the apparatus, may cause small cracks in the casing and leakage of the -impregnating material. Y

The object of the invention is to obviate this dimculty by illling the i'ree space between the casing and the electrical apparatus proper with a viscous electrically. insulating material which on exposure to air through leaks in the casing congeals at such a rate that the said leaks are automatically sealed substantially without any loss oi insulating material.

The invention oilers the advantage that the said danger is avoided and that moreover a less perfect and consequently simpler seal of the casing may be initially provided. l

The insulating material of the invention may be insulating air-drying iacquers, comprising for example as a base, an air-drying oil.

By way of example we quote below a compo-A sition especially suited for use in carrying out the invention. A mixture of 1 part of colophony andlpartoidammarreainisheatedatatemperature of about 300 C. The greater part of the gaseous products thus produced is separated by distillation and to the mixture there is added sulllcient zinc oxide to neutralise the free acids. To the molten resin mixture thus obtainedthereisaddedamixtureotparts of wood oiland 1% parts o! linseedoil, which resultingmixtureisthenmaintainedatatemperature o! 270 C. for about hal! an hour, and subsequently cooled. l

Por the purpose of the invention automatic sealingistobeunderstoodtomeanthatthere occurs nibstantially no loss of insulating materialwhenthevhoousmaterlalise'xposedtoalr at20C.underahydrostaticpressureof4grs. per square cm; through an aperture having a lcngthoi1rimandadiametel'ofiizmm.-

The invention is particularly important in connection with transformers which are used for generating very high voltages since, as is wellknown, a liquid or semi-liquid impregnating material is generally more resistant against such high voltage in the course of time than a solid or a more or less brittle material.

When carrying the invention into practice the form ot wire insulation used in the electrical apparatus is to be taken into account and liquids, particularly aromatic liquids, having a high dissolving power should generally be avoided if the electricalI apparatus contains the usual forms oi enamel wire.

In the single iigure of the drawing forming part of the speciilcation there is shown, partly in cross-sectional view, a transformer assembly comprising a metal container l0, a transformer ll (shown in block form) and an electrically insulating' liquid I2 filling the container and impregnating and surrounding the transformer. The insulating liquid l2, consisting for example, of the material above specifically described. has the property of congealing when exposed to air at such a rate as to automatically seal leaks, for example, as shown at i3, which occur in the container.

'Ihe windings of the transformer are connected to insulated bushings It secured in the cover of the container and by which external electrical connections may be made to the transformer.

What we claim is: 1

Electrical apparatus comprising a container subject to leaks, an electrical insulating liquid within the container, and an electrical device immersed in the liquid, said liquid consisting o! substantially a mixture of the reaction product of approximately-one partcolophony and one parifdammar resin, zinc oxide in an amount sufncient to neutralize the free acids ot said reaction 4o product and a mixture of approximately tour partswoodoilandonepartlinseedolLsaid liquid having the propertyoicongeals when incontactwlthairatsucharateasaaautomatically theoontainerleakswitbatany 4s substantielles or me matins liquid.

GILLIS H0181'.

JOHANNB HKBTR-s. 

